Yet another plant tank design

To: Aquatic-Plants at actwin_com
Subject: Yet another plant tank design
From: Kevin Conlin <kcconlin at cae_ca>
Date: Mon, 02 Oct 1995 13:51:48 -0400
Having been hopelessly confused by the discussions on substrates,
cation-exchange capability, and the like, I thought it might be
interesting to try and eliminate the substrate altogether (hydroponic
plants are normally grown with bare roots anyway).  This led to the
following design:

                           Aeration chamber

                        |                    |      
          ---------------      Nutrient      ---------------
          | _____________   -> Water Flow -> _____________ |
          | |           |____________________|           | |
          | |                                            | |
   |      | |                                            | |     |
   |    -------                                          | |     |
   |--- |     | ------- Water Line --------------------- | | ----|
   |    |     |                                          | |     |
   |    |______                                          | |     |
   |      | |   Powerhead                                | |     |
   |      | |                                            | |     |
   |      | |                                            | |     |
   |      | |                                            | |     |
   |      | |                                            | |     |
   |      | |                                            | |     |
   |      | |                                            | |     |
   |----- | | ------------2" Gravel -------------------- | | ----|
   |      | |                                            | |     |
   |_ _ _ | |_ _ _ _ _ _ _ Fine Mesh _ _ _ _ _ _ _ _ _ _ | |_ _ _|
   |                                                             |
   |                    2" Root Growth Area (no gravel)          |
   |_____________________________________________________________|


Plant roots grow through the fine mesh into the aerated nutrient
solution circulating below the gravel.  Relatively few nutrients
(hopefully) will make it past the mesh, through the gravel, and into
the water.  Nutrients that escape will be sucked up by hornwort or
duckweed or something similar.  Oxygen diffusion from top & bottom
would keep the gravel (or even sand) from becoming anoxic.  An
ordinary canister filter would take care of the water above the
gravel.

The fine mesh could be standard UGF filter plates (the square interlocking
kind) or even plastic speaker grill, supported by short lengths of PVC pipe.
Any open plastic container would work as the aeration chamber, which could
contain bioballs or something similar depending on the degree of aeration
desired.  A valve of some sort at the outlet of the powerhead could be used
to decrease the flow rate of the nutrient solution.  As for the solution
itself, just add your favorite fertilizer to the aeration chamber at the
recommended intervals and monitor iron and nitrate as usual.

Comments?
--
Kevin Conlin   Montreal, Canada   "We're Canadians.  We HAVE to be polite"